1. Field of Invention
The invention relates to a semiconductor integrated circuit chip with a nano-structure-surface passivation film and a method of fabricating the same, and more particularly to a method of fabricating a semiconductor integrated circuit chip, which has a nano-structure-surface passivation film and is free from encountering any external interference, and the semiconductor integrated circuit chip formed using this method. The invention is extended from the commonly assigned U.S. patent application Ser. No. 10/989,510 (US20050110051A1), filed on Nov. 17, 2004, and entitled “SURFACE PROCESSING METHOD FOR A CHIP DEVICE AND A CHIP DEVICE FORMED BY THE METHOD”.
2. Related Art
The method of manufacturing a chip in the field of the semiconductor manufacturing processes usually has to consider the electrical property provided by the chip, and to package the chip in a package body by packaging procedures so as to get rid of any possible damage caused by external forces such as the pressure and the electrostatic discharge.
However, with the development of the chip application field, the new application needs to expose a portion of a chip surface to the environment. For example, a chip-type fingerprint sensor must have a chip surface for contacting a finger to read the fingerprint of the finger for the identification.
Thus, the mechanical property of the chip surface has to be considered to provide a surface with wear-resistant, pressure-resistant, hydrophobic, oleophobic and contamination-resistant properties.
Conventionally, a basic structure of a capacitive fingerprint sensing chip includes a silicon substrate in which associated sensing and control processing circuits are formed. A plurality of metal plates serving as sense electrodes are arranged in an array on the surface of the chip. Herein, the sense electrodes, the sensing and control processing circuits, and the silicon substrate are referred to as a substrate structure. In addition, a dielectric material layer serving as a dielectric material of a sense capacitor and an exposed protection layer for the chip is formed on an outermost surface of the chip. In order to achieve the pressure-resistant and the wear-resistant properties of the chip surface, the prior art adopts a hard dielectric material to serve as the outermost protection layer, as disclosed in WO 01/06448A1, WO 03/098541A1, U.S. Pat. No. 6,091,082, EP1256899, U.S. Pat. No. 6,114,862 and U.S. Pat. No. 6,515,488. In brief, the prior art inventions usually have a hard material layer, such as a silicon dioxide layer, a silicon nitride layer or a silicon carbide layer, formed above the substrate structure.
The silicon dioxide and the silicon nitride are the hydrophilic and oleophilic materials that form hydrophilic and oleophilic surfaces, on which the finger oil or finger sweat is easily remained as a latent fingerprint when the sensor is used. The silicon carbide material has a better hydrophobic property but still is an oleophilic material. So, the latent fingerprint problem from the finger lotion or oil contamination still exists. Furthermore, when the above-mentioned materials are deposited, the surface roughness cannot be easily controlled to reduce the surface wetting effect. Therefore, a CMP (Chemical Mechanical Polishing) process has to be performed to get a smooth surface and reduce the wetting effect of the sensor surface, on which the latent finger problem is minimized. This, however, may increase the manufacturing complexity and cost. A method for filling the silicon dioxide into a plurality of small voids and thus obtaining a smooth external surface by depositing the silicon dioxide and then performing the CMP process has been disclosed in U.S. Pat. No. 6,515,488 to Thomas. However, the manufacturing processes are too complicated and are not suitable for the typical manufacturing processes of the commercial wafer foundry.
In U.S. Pat. No. 6,762,470 patent, Siegel et. al. disclose a design having a Teflon material formed on the chip surface in order to solve the problem of the hydrophobic, oleophobic and contamination-resistant surface properties. However, Teflon (the Trademark of DUPONT) is a fluorocarbon (FC) polymer, which cannot be effectively bonded to the material, such as the silicon dioxide and the silicon nitride formed on the surface of the semiconductor chip, having the higher surface energy. So, after multiple times of fingerprint test rubbing, this kind of material tends to detach from the fingerprint sensor.
In order to solve this problem, the present inventors disclose a best material choice of bonding a silane group to the other end of the fluorocarbon (FC) polymer in the US20050110051A1 patent. This is because the Si—O—CH3 or Si—O—C2H5 in the silane group tends to be hydrolyzed into Si—O— or Si—OH group. This group and the silicon dioxide or silicon nitride on the surface of the semiconductor chip can form covalent bond or hydrogen bond of “—Si—O—Si—” or “Si—O—H” with the high bonding intensity.
In order to facilitate the manufacture and the production, the above-mentioned method prepares the polymeric monomers in the form of solution, which is applied to the surface of the semiconductor chip surface by way of immersion, spin coating or spray coating. Then, a high temperature (greater than 60 degrees centigrade) and high humidity (90%) environment is provided to facilitate the polymerization and curing.
However, one main drawback of this method is that the manufacturing and curing processes of the polymeric monomers only can form the thickness of the molecular layer on the chip surface. That is, the maximum thickness thereof is only several tens of nanometers, and the layer will be scraped due to the improper use of the chip, thereby deteriorating the effect of resisting the contamination.
Furthermore, because the uneven surface of the chip may be formed when the chip is being manufactured, it is impossible to form an even surface even if the method of the US20050110051A1 patent is adopted. Similarly, contamination tends to be accumulated in the voids of the chip surface.
Most important of all, electronic products containing the halogen compound will be prohibited in order to meet the environment protection requirement in the future. Thus, the method using the fluoride to improve the hydrophobic, oleophobic and contamination-resistant surface properties of the chip surface may induce a great environment protection problem.
The invention provides another solution in order to extend the spirit of the US20050110051A1 patent mentioned hereinabove, to avoid the contamination of the chip surface, and to solve the problems encountered in the US20050110051A1 patent.